won;t rev past 2000 rpm?

[johntom]

Hi my '87 350i won't rev past 2000rpm. Foulishly i changed the Dist cap., rotor arm, the fuel filter and the fuel pump at once before running the car, previously it ran fine! After i fitted the new Bosch pump the car wouldn't start so i changed back to the old pump (bought the new one because the old one was scabby) - new pump faulty, car started. I ran the car today and it won't rev past 2000rpm sometimes it cuts out at 2000rpm, however it started from cold fine. The HT leads are definitely in the right position, any ideas?
many thanks

[GreenV8S]

Suggest you put back the original HT components (assume it was previously working OK with them), and if the filter is directional check you have it the right way round.

[johntom]

Hi
the filter is directional and the right way round. Unfortunatley i have binned the original dist cap and rotor arm. How do i tell if the fault is fuel or electric?

[grahamw48]

See if you have a (strong) spark, starting at the coil and working through to plugs.

Also check low tension wires at coil and dizzy are correct way round and well connected

See if you have fuel. Plugs should be wet if it's lack of sparks and fuel arriving ok.

Sounds like something has just been connected the wrong way round or just left off.

You'll be kicking yourself.

[johntom]

Hi
i have just remembered that after fitting the filter etc i used a can of old fuel to start the engine?
I will drain that off and try some new. I have checked for anything loose or not connected but haven't found anything. The engine starts ok and runs fine upto around 2000rpm, at 2000rpm it seams to cut out/sputter.
thanks

[dwgriffith]

It's quite common for the distributor upper shaft to be pulled out of position when changing the rotor arm, the effect is the weight's can no longer move out and the timing gets messed up big time with increasing RPM.

Edited by dwgriffith on Monday 26th May 21:22

[johntom]

Hi
the rotor arm was very difficult to remove, so i could have disturbed something. Is it fixable if i have messed it up as you described.

[GreenV8S]

You can test the mechanical advance by twisting the rotor clockwise - it should spring back to the rest position.

[Jack Valiant]

This sound like you have disturbed the bob wieghts in the dizzy. Make sure the springs are still on as they do come off if you had to yank the rotor arm off.

Chris

[johntom]

Hi

if i turn the rotor arm clockwise it turns and springs back to it's rest position.
Where are the springs, do i have to remove the whole thing, or are they under the plastic cap beneath the rotor arm?
thanks

[GreenV8S]

johntom said:

if i turn the rotor arm clockwise it turns and springs back to it's rest position.

That proves the mech advance mechanism is intact and the springs are connected correctly. You could also prove this empirically by connecting a timing strobe light watching the ignition timing advance with revs.

[johntom]

Could contaminated fuel cause this type of problem?

[350zwelgje]

johntom said:

Could contaminated fuel cause this type of problem?

I think you should have problems all over the place in that case.
Tend to agree with distributor comments made before.
Other could be the fuel pump as you were out to replace it.
Seems you wanted another pump, so would get a good one if I were you. If not sorted, have a look at that distributor and check the timing. Thinking about that it is worth checking the timing now as well.

Question I ask myself is if mixing the ignition sequence up could that cause it as well? Think so on a V8. Then it would be worth double checking the leads to the plug for it.

Hope you sort it soon.

Rob

Edited by 350zwelgje on Tuesday 27th May 21:00

[johntom]

I have replaced the fuel filter and added fresh fuel just to rule out the posibility of the other fuel being contaminated. Still no difference, the car revs to 1800 rpm them seams to shudder and drop back, a bit like a rev limiter.

Could it be the distributor weights if the rotor turns and springs back to the rest position?
Would the car still run if the leads were in the wrong order on the dist. cap (although i have checked them with the diagram in the 'bible')?
many thanks

[GreenV8S]

Check the air flow meter out and make sure you get a good reading from it back at the ECU connector.